alt Hacker Newsfor me, at least, one interview process being 9 hours isn't a big deal and i agree with you that a company doing that is likely to have a more coherent culture and make smarter hiring decisions.
the problem is that when the job market isn't too hot, you might be applying to a dozens or even a hundred+ positions. if 5-10 of those all have 9 hour processes, well now you have 1-2 full weeks work of unpaid interviewing to do, which is a lot to organize, prepare for, etc.
The only time I see people blitzing interviews and stacking 5-10 different companies interview processes is when they’re unemployed urgently trying to change jobs. In those cases it makes sense to do whatever you need to do to stack interviews.
For normal job changing, people are more selective and interview maybe a couple times per year, spread out over time. In my experience it hasn’t been hard at all to get 3 hours here and there for interviews. Tech company culture is usually forgiving about people leaving for appointments and other things so this isn’t nearly as hard as it is for some of my friends in other careers where it’s PTO every time.
I’ve also not actually seen many cases where people schedule 10 interviews at once and actually get the full interview experience at every one of them. People get rejected at earlier stages of the interview process or they start pulling out if they realize the job isn’t a good fit. It would be very rare for someone to schedule 10 interviews and actually invest the maximum time into every single one of them.
So I understand your concern, but in my observation this pattern doesn’t really happen. People have been doing much more involved interviews (travel, flights, hotels) for decades.